Non-elastomeric, non-polymeric, non-metallic membrane valves for semiconductor processing equipment

ABSTRACT

Non-elastomeric, non-polymeric, non-metallic membrane valves for use in high-vacuum applications are disclosed. Such valves are functional even when the fluid-control side of the valve is exposed to a sub-atmospheric pressure field which may generally act to collapse/seal traditional elastomeric membrane valves.

INCORPORATION BY REFERENCE

An Application Data Sheet is filed concurrently with this specificationas part of the present application. Each application that the presentapplication claims benefit of or priority to as identified in theconcurrently filed Application Data Sheet is incorporated by referenceherein in its entirety and for all purposes.

In semiconductor processing operations, it is often necessary to providea multitude of gases that may be flowed into a semiconductor processingchamber in various combinations, at various flow rates, and at varioustimes. In some semiconductor processing tools, it is not uncommon tofind as many as 15-20 different gases being supplied to the tool, witheach gas typically being separately controlled. Semiconductor processingtools typically include “gas boxes” that house a large number ofdifferent computer-controlled valves, mass flow controllers, and/orother gas-flow components that may be controlled to provide desiredmixtures of gases at various times during semiconductor processingoperations.

It is typical for such gas boxes to be assembled out of discretecomponents, e.g., surface-mount valves, manifold channels, seals, etc.,that are relatively large, e.g., that feature, for example, 1.5″ squaremounting flanges for interfacing the flow components with theirrespective manifolds. Such components may be assembled together into a“gas stick” for each gas to be controlled, and the gas sticks thenmounted into a cabinet to form the “gas box.” A gas stick may includemultiple surface-mount components, e.g., 5 to 10 such components, andsemiconductor processing tools may include multiple, e.g., 10 or 20, ofsuch gas sticks.

Presented herein are new designs for semiconductor processing gas flowcontrol components that may be used to provide a much more compactvalving system.

SUMMARY

Details of one or more implementations of the subject matter describedin this specification are set forth in the accompanying drawings and thedescription below. Other features, aspects, and advantages will becomeapparent from the description, the drawings, and the claims. Thefollowing, non-limiting implementations are considered part of thedisclosure; other implementations will be evident from the entirety ofthis disclosure and the accompanying drawings as well.

In some implementations, an apparatus may be provided that includes asubstrate having one or more microfluidic valve structures, eachmicrofluidic valve structure of the one or more microfluidic valvestructures including a diaphragm, the diaphragm having a nominaldiameter D_(d), a first side, and a second side opposite the first side;a base; an orifice in the base, the orifice having cross-sectional areaA_(o) in a plane parallel to the base; and a raised seat structure, theraised seat structure having a nominal outer diameter D_(o) and anominal inner diameter D_(i), For each microfluidic valve structure insuch an apparatus, the diaphragm may be made from a non-elastomericmaterial, the raised seat structure may extend from the base towards thefirst side of the diaphragm, a surface of the raised seat structurefacing the diaphragm may be separated from the first side of thediaphragm by a gap of distance d when the microfluidic valve structureis in an unactuated state, D_(i) may be less than or equal to 0.2·D_(d),A_(o) may be less than or equal to

$\frac{d \cdot D_{i} \cdot \pi}{2},$

and the diaphragm, the raised seat structure, and the gap of thatmicrofluidic valve structure may be sized such that, when thatmicrofluidic valve structure is transitioned to an actuated state bypressurizing the second side of the diaphragm to a first pressure, aportion of the diaphragm is caused to elastically deform towards, andseal against, the raised seat structure.

In some such implementations, for one or more of the microfluidic valvestructures, A_(o) may be less than or equal to

$\frac{d \cdot D_{i} \cdot \pi}{2}$

and A_(o) may be greater than or equal to

$0.9{\frac{d \cdot D_{i} \cdot \pi}{2}.}$

In some other such implementations, for one or more of the microfluidicvalve structures, A_(o) may be less than or equal to

$\frac{d \cdot D_{i} \cdot \pi}{2}$

and A_(o) may be greater than or equal to

$0.8{\frac{d \cdot D_{i} \cdot \pi}{2}.}$

In some other such implementations, for one or more of the microfluidicvalve structures, A_(o) may be less than or equal to

$\frac{d \cdot D_{i} \cdot \pi}{2}$

and A_(o) may be greater than or equal to

$0.7{\frac{d \cdot D_{i} \cdot \pi}{2}.}$

In some other such implementations, for one or more of the microfluidicvalve structures, A_(o) may be less than or equal to

$\frac{d \cdot D_{i} \cdot \pi}{2}$

and A_(o) may be greater than or equal to

$0.6{\frac{d \cdot D_{i} \cdot \pi}{2}.}$

In some other such implementations, for one or more of the microfluidicvalve structures, A_(o) may be less than or equal to

$\frac{d \cdot D_{i} \cdot \pi}{2}$

and A_(o) may be greater than or equal to

$0.5{\frac{d \cdot D_{i} \cdot \pi}{2}.}$

In some other such implementations, for one or more of the microfluidicvalve structures, A_(o) may be less than or equal to

$\frac{d \cdot D_{i} \cdot \pi}{2}$

and A_(o) may be greater than or equal to

$\frac{d \cdot D_{i} \cdot \pi}{2 \cdot 625}.$

In some implementations, for a first microfluidic valve structure of theone or more microfluidic valve structures, a maximum distance along afirst axis between the first side of the diaphragm for the firstmicrofluidic valve structure and the surface of the raised seatstructure for the first microfluidic valve structure may be less than orequal to 40 μm, and the first axis may be perpendicular to the surfaceof the raised seat structure for the first microfluidic valve structure.

In some implementations of the apparatus, the first side of thediaphragm for a first microfluidic valve structure of the one or moremicrofluidic valve structures may be subjected to a pressure at or belowatmospheric pressure and the second side of the diaphragm of the firstmicrofluidic valve structure may be subjected to atmospheric pressurewhen the first microfluidic valve structure is in the unactuated state.

In some implementations of the apparatus, the first pressure for thefirst microfluidic valve structure may be above atmospheric pressure.

In some implementations of the apparatus, the diaphragm for at least oneof the one or more microfluidic valve structures may be made fromsilicon or silicon dioxide.

In some implementations of the apparatus, at least one of the one ormore microfluidic valve structures may be made from multiple layers ofsilicon or silicon dioxide.

In some implementations of the apparatus, the apparatus may beconfigured to be connected to a gas supply such that at least a firstmicrofluidic valve structure of the one or more microfluidic valvestructures is part of a flow path within the apparatus that isconfigured to be fluidically connectable with the gas supply such thatthe raised seat structure for the first microfluidic valve structure isfluidically interposed between the gas supply and the diaphragm for thefirst microfluidic valve structure.

In some such implementations of the apparatus, the apparatus may furtherinclude the gas supply, and the apparatus may be connected to the gassupply such that the raised seat structure for the first microfluidicvalve structure is fluidically interposed between the gas supply and thediaphragm for the first microfluidic valve structure.

In some implementations of the apparatus, the apparatus may furtherinclude a diaphragm layer, an actuator plenum layer, and a valve plenumlayer. In such implementations, the diaphragm of a first microfluidicvalve structure of the one or more microfluidic valve structures may beprovided by the diaphragm layer, a first side of the diaphragm layer mayprovide the first side of the diaphragm of the first microfluidic valvestructure, a second side of the diaphragm layer may provide the secondside of the diaphragm of the first microfluidic valve structure, thefirst side of the diaphragm layer may be bonded to the valve plenumlayer, the second side of the diaphragm layer may be bonded to theactuator plenum layer, the actuator plenum layer may have a hole throughit with a diameter D_(apl) that is centered on the diaphragm of thefirst microfluidic valve structure, the valve plenum layer may have ahole through it with a diameter D_(vpl) that is also centered on thediaphragm of the first microfluidic valve structure, and D_(vpl) may beless than D_(apl).

BRIEF DESCRIPTION OF THE DRAWINGS

The various implementations disclosed herein are illustrated by way ofexample, and not by way of limitation, in the figures of theaccompanying drawings, in which like reference numerals refer to similarelements.

FIG. 1 depicts an example apparatus with a non-elastomeric,non-polymeric, non-metallic microfluidic valve structure.

FIGS. 2 through 4 show Mach numbers in an orifice for a non-elastomeric,non-polymeric, non-metallic microfluidic valve structure under variousflow conditions for two different arrangements of such valve structures.

FIG. 5 provides a simplified perspective view of various elements of amicrofluidic valve structure.

FIG. 6 depicts a diagram of a flow splitter for combining a plurality ofgases together in a controllable manner.

FIG. 7 depicts an example of a two-source flow splitter.

The Figures herein are generally not drawn to scale, although variousaspects of the Figures, e.g., as discussed below, may be drawn to scale.

DETAILED DESCRIPTION

Modern semiconductor processing tools often utilize a large number ofdifferent processing gases that are introduced to a semiconductorprocessing chamber at different times, in different combinations, and atdifferent flow rates. In some modern semiconductor processing tools,some reactant gases may be flowed in an alternating fashion, with eachsequential flow of reactant gas being followed by a flow of inert orpurge gas that is used to sweep out any remnants of that reactant priorto the flow of a subsequent reactant. This prevents the two reactantsfrom mixing within the gas distribution system, which may produceundesirable side effects (although such mixing may be desirable once thereactant gases are within the semiconductor processing chamber). Oneissue with traditional gas control component usage is that the flowpaths involved are often long and may include significant lengths thatare in between the last controllable flow component for a given gassupply and the point where the gas is flowed into the semiconductorprocessing chamber. The gas that is trapped in such a flow path may bewasted.

In order to provide a more compact, low-cost solution for gas flowcontrol in semiconductor processing tools, the present inventorsconceived of new types of non-elastomeric, non-polymeric, non-metallicmembrane valves. Such membrane valves may, in some respects, be somewhatsimilar to elastomeric microfluidic membrane valves used, for example,in microfluidic cartridges or other liquid-base analysis systems.However, due to the operating pressures typically seen in semiconductorprocessing systems, as well as the often highly toxic or reactivereactant gases typically handled by such systems, microfluidic valvetechnology that is frequently used for liquid-based microfluidichandling, e.g., such as may be used in genetic sequencing systems, isnot suitable. For example, elastomeric microfluidic valves that arecommonly used in microfluidic applications for chemical and biologicalanalysis may be susceptible to chemical attack or gas permeation throughthe elastomeric membranes used in such valves. Moreover, since mostsemiconductor processing chambers are operated at sub-atmosphericpressures, it may often be the case that the downstream pressureenvironment for such valves, and thus the side of such elastomericmembranes that provides the sealing in such valves, would be at areduced pressure compared to the other side of such membranes, whichwould generally cause such elastomeric membranes to deform into a“sealed” state and be difficult or impossible to reliably open.

To address such issues, the present inventors conceived ofnon-elastomeric, non-polymeric, non-metallic membrane valves in whichthe valves are made of layers of non-elastomeric, non-polymeric, andnon-metallic materials that are bonded together to form a layered stack.Such materials may be selected so as to be non-reactive with the gasesthat are flowed through such valves, e.g., silicon (e.g., glass) orsilicon dioxide (e.g., quartz). By avoiding the use of polymeric andelastomeric materials, the issues with potential gas permeation throughthe membranes of such valves are avoided; avoiding the use of metallicmaterials reduces the risk of adverse chemical reaction between thevalve material and the processing gases that may be handled by thevalves.

In an elastomeric membrane valve, a thin elastomeric membrane layer istypically overlaid on a substrate that has an inlet port and an outletport that may be sealed by the elastomeric membrane layer when theelastomeric membrane layer is in contact with the substrate. In somesuch valves, there may be a spacer layer in between the elastomericmembrane and the substrate that results in a gap between the elastomericmembrane and the substrate when the elastomeric membrane is in anundeformed state, thereby allowing for liquid or gas to flow from oneport to the other; when pressure is applied to the side of theelastomeric membrane opposite the gap, the elastomeric membrane deflectstowards and contacts the inlet port and the outlet port, thereby sealingthem. In other such valves, the elastomeric membrane may be flushagainst the substrate when undeformed, thereby sealing the inlet portand the outlet port. When the side of the elastomeric membrane oppositethe side that is sealed against the inlet and outlet is subjected to areduced pressure, the elastomeric membrane may be caused to distendupwards, thereby allowing fluid to flow from the inlet to the outlet.When the actuation pressure (or negative pressure) is removed, theelastomeric membrane returns to its undeformed state. Elastomericmaterials, e.g., silicone, are typically used in such valves since suchmaterials are liquid-tight (and most microfluidic systems are used totransport liquids), robust, and capable of undergoing large strainswithout permanent deformation or rupture. This makes such elastomericmembranes a relatively ideal choice in most cases, as the pliability ofthe elastomeric membrane material allows it to conform to the interiorsurfaces of the valve structure, thereby achieving a very good sealagainst the inlet and outlet ports, and can withstand repeatedactuations and relatively large-scale deflections. Microfluidic valveswith elastomeric membrane valves may also have a generally rigidstructural layer or layers in addition to the elastomeric membrane layerthat provides overall rigidity to the valve structure. Such rigidstructural layers may, for example, be provided by non-elastomericpolymeric materials, e.g., acrylic or polycarbonate, or bynon-elastomeric, non-polymeric materials, such as glass.

In the present non-elastomeric, non-polymeric, non-metallic membranevalves, however, the entire wetted valve structure (i.e., the portionsof the valve that come into contact with the fluid flow that the valveis designed to control), including the membrane, may be made fromnon-elastomeric, non-polymeric, and non-metallic materials. Inparticular, materials such as silicon (glass) or silicon dioxide(quartz) may be used, both of which are largely non-reactive with mostsemiconductor processing gases. While such materials provide goodresistance to chemical attack, glass and quartz are both very brittlematerials, which severely limits their usefulness in a membrane valvecontext.

The most noticeable issue with using non-elastomeric, non-polymeric,non-metallic materials is that such materials are typically much stifferthan elastomeric materials, thereby limiting the amount of travel that amembrane made of such materials may experience in response to applying agiven pressure differential to it. Moreover, most such materials thatare well-suited for use with the various gases used in semiconductorprocessing equipment, e.g., materials that are largely non-reactive withsuch gases (such as silicon and quartz), may have very low plasticityand may fracture if subjected to excessive flexure. In contrast,elastomeric materials, due to their stretchy and compliant nature, areable to undergo radical deformation without fracturing.

FIG. 1 depicts an example apparatus with a non-elastomeric,non-polymeric, non-metallic microfluidic valve structure. In FIG. 1 ,the apparatus 100 is implemented in a substrate 102, in which multiplepatterned layers 104, e.g., layers 104 a-104 g, are arranged to providea microfluidic valve structure 106. The number and arrangement of layers104 may vary from what is depicted, and it will be understood that anyarrangement of layers that may arrive at structures with characteristicssimilar to those discussed here falls within the scope of thisdisclosure. These layers may be bonded together using any suitablebonding technique, e.g., diffusion bonding, fusion bonding, etc.

The layers 104 of the substrate 102 may be configured to provide adiaphragm 108, e.g., a thin, circular region, that may serve as aflexible membrane interposed between an actuator plenum 132 and a valveplenum 138. The diaphragm 108 may have a first side 110 and a secondside 112, as well as a nominal diameter D_(vpl). The valve plenum 138may generally be defined as an open volume sandwiched between the firstside 110 and a base 114 and bounded by an outer perimeter of thediaphragm 108. The valve plenum 138 may include a raised seat structure120 that may protrude up from the base 114 and extend towards the firstside 110 of the diaphragm 108. The raised seat structure 120 may, forexample, form a continuous wall about a central region thereof, and havea surface 122 that faces towards the first side 110 of the diaphragm108. In some implementations, such as that shown in FIG. 1 , the raisedseat structure 120 may be an annular wall that extends from the base 114up towards the first side 110 of the diaphragm 108.

An orifice 118 may be located within the central region of the raisedseat structure 120, e.g., located in the center of the central region ofthe raised seat structure 120, and may pass through the base 114. Theorifice 118 may also be located at other locations within the centralregion of the raised seat structure 120, e.g., at locations within thecentral region of the raised seat structure 120 that are not centered onthe raised seat structure 120. The orifice 118 may fluidically connectthe valve plenum 138 with a gas inlet 124, which may be used to supply asemiconductor processing gas from a gas supply (not shown) to themicrofluidic valve structure 106. The valve plenum 138 may befluidically connected with an outlet port 116 through which processinggas may flow when the microfluidic valve structure 106 is in an openstate and the gas inlet 124 is fluidically connected with a gas supplyfor such a processing gas. The orifice 118 may have any desiredcross-sectional shape, although in the examples discussed herein, theorifice 118 has a circular cross-sectional shape of diameter D.

Control for the microfluidic valve structure 106 may be provided throughany suitable mechanism for causing the diaphragm 108 to flex. Forexample, the actuator plenum 132 may be interfaced with a controllablepneumatic source, e.g., a valve attached to a pressurized air source,that allows the actuator plenum 132 to be controllably pressurized,thereby causing the diaphragm 108 to flex and distend into the valveplenum 138, thereby causing the first side 110 of the diaphragm 108 tomove towards the surface 122. When the diaphragm 108 is sufficientlydistended, the first side 110 of the diaphragm 108 may contact thesurface 122, thereby sealing the raised seat structure 120 andpreventing further flow of gas from the orifice 118 and out of theraised seat structure 120. When the microfluidic valve structure is inan unactuated state, the first side 110 and the surface 122 may beseparated by a gap 126 of distance d.

The microfluidic valve structure pictured in FIG. 1 may be usedregardless of flow direction (e.g., with gases flowing in the directionindicated, or with gases flowing in the opposite direction). However, inscenarios in which the orifice 118 is fluidically interposed between asupply of gas and the diaphragm 108, the upstream placement of theorifice 118 relative to the diaphragm 108 may provide a significantadvantage. The term “fluidically interposed,” as used herein, refers toa condition where a first structure in a fluidic flow system ispositioned relative to two second structures in the fluidic flow systemsuch that fluid flowing from one of the second structures to the othersecond structure must necessarily come into contact with, or flow by,the first structure prior to reaching the other second structure. Forexample, a kitchen sink would be described as being fluidicallyinterposed between the kitchen faucet for that sink and the drain forthat sink. Similarly, a house's main water shut-off valve would bedescribed as being fluidically interposed between a water main in thestreet and the interior plumbing of the house.

As gas flows through the microfluidic valve structure 106 in the mannerdepicted, it may encounter two general regions of increased flowresistance. The first region is the orifice 118, which may generally besized to act as a sonic flow restrictor, e.g., configured such that gasflowing through the orifice 118 develops into sonic, fully choked flow,i.e., M=1, within the orifice 118. If the dimensions of the orifice 118are tightly controlled, as may be achieved through lithographictechniques, it may be possible to achieve very precise orificedimensions. Such precise dimensional control, coupled with fully chokedflow, may allow for very precise time-based metering of gas flow throughthe microfluidic valve structure.

The second region is in the annular region sandwiched between thesurface 122 and the first side 110 and having a height defined by thegap 126. This region may have a flow resistance that is governed inlarge part by factors such as the inner (D_(i)) and outer (D_(o))dimensions, e.g., inner and outer diameters, of the raised seatstructure 120, as well as the gap distance d.

If the gas flow is in the opposite direction from that shown in FIG. 1 ,i.e., with the diaphragm 108 fluidically interposed between the gassupply and the orifice 118, the diaphragm 108, and the annular gapbetween the diaphragm 108 and the surface 122 of the raised seatstructure 120, will be upstream of the orifice. In such a scenario, ifchoked flow occurs in the region between the diaphragm 108 and thesurface of the raised seat structure 120, then choked flow willgenerally not develop at the orifice 108 downstream. In such a scenario,the orifice 118 is no longer an effective mechanism for controlling ormetering gas flow and becomes superfluous. The mass flow rate throughthe annular gap at choked flow may be influenced by various factors,including the gap distance d between the diaphragm 108 and the surface122 of the raised seat structure 120, the inner diameter D_(i) of theraised seat structure 120, and the radial thickness of the raised seatstructure 120 (0.5·(D_(o)−D_(i))). Two of these factors may becontrolled through manufacturing tolerances, but it is difficult tocontrol the gap distance d, as this value may fluctuate during usedepending on, for example, pressure conditions within the valve plenum138 and/or atmospheric pressure conditions.

Additionally, it may generally be desirable to generally reduce the gapdistance d since the smaller the distance d is, the smaller the gap isthrough which the diaphragm must be displaced in order to contact thesurface 122 of the raised seal structure 120. Given the limitedflexibility of non-elastomeric, non-polymeric, non-metallic materials,e.g., quartz or glass, the range of motion that a diaphragm 108 made ofsuch material may provide for a given size of diaphragm may be quitelimited.

Thus, for a configuration where the diaphragm 108 is fluidicallyinterposed between the gas supply and the orifice 118, the microfluidicvalve structure may either use a large gap size, which may require alarger diameter diaphragm but may avoid potential choked flow in theannular gap area, or a small gap size, which allows for a smallerdiameter diaphragm but may increase the chance that choked flow willoccur in the annular gap instead of the orifice 118 (an attempt may alsobe made to size the gap “just right,” but since the gap size mayfluctuate with environmental conditions, e.g., due to the ambientpressure environment, such efforts may not produce reliableperformance).

If one configures the diaphragm 108, orifice 118, and gas supply assuggested by FIG. 1 , however, with the orifice 118 fluidicallyinterposed between the gas source and the diaphragm 108, then chokedflow through the orifice 118 may be produced for a given flow regimewith a much smaller gap distance d than may be utilized in the oppositearrangement.

For example, in fluid simulations performed on an example orifice 118with a diameter d=0.3 mm and a raised seat structure 120 having adiameter D_(i)=1 mm for a flow of 10 standard cubic centimeters perminute (SCCM) of argon, it was observed that the Mach number for flowthrough the orifice 118 remained relatively constant at 1 for a range ofgap sizes from 0.005 mm to 1 mm when the orifice was fluidicallyinterposed between the gas source and the diaphragm, but in an identicalconfiguration where the diaphragm was fluidically interposed between thegas source and the orifice, the Mach number for flow through the orifice118 remained similarly constant at 1 for gap sizes larger than 0.2 mm,but rapidly dropped to 0.01 for gap sizes between 0.005 mm and 0.2 mm.FIG. 2 shows a plot of such behavior (Orifice Upstream=orificefluidically interposed between the gas source and the diaphragm; OrificeDownstream=diaphragm fluidically interposed between the gas source andthe orifice). From this simulation data, it can be seen that positioningthe orifice such that it is fluidically interposed between the gassource and the diaphragm permits the use of gap distances d as low as−0.005 mm without loss of choked flow in the orifice 118, whereasfluidically interposing the diaphragm between the gas source and theorifice requires a gap distance d of −0.2 mm or more to ensure thatchoked flow occurs within the orifice.

FIGS. 3 and 4 depict similar plots of simulation data. FIG. 3 depicts aplot of a simulation similar to that of FIG. 2 , except that the exampleorifice 118 had a diameter d=0.5 mm, the raised seat structure 120 had adiameter D_(i)=1 mm, and a flow of 30 standard cubic centimeters perminute (SCCM) of argon was introduced through the microfluidic valvestructure 106. Similarly, FIG. 4 depicts a plot of a simulation similarto that of FIG. 2 , except that the example orifice 118 and the raisedseat structure 120 both had diameters D_(i) and D=1 mm, and a flow of120 standard cubic centimeters per minute (SCCM) of argon was introducedthrough the microfluidic valve structure 106. In both of theseadditional cases, similar behavior may be observed, i.e., positioningthe orifice such that it is fluidically interposed between the gassource and the diaphragm permits the use of much smaller gap distancesd, e.g., 0.01 mm or 0.05 mm, while still maintain choked flow conditionsin the orifice 118, whereas positioning the diaphragm such that it isfluidically interposed between the gas source and the orifice requiresthat the gap distance d be kept, for example, to 2.5 mm or higher (forthe scenario of FIG. 3 ; for the scenario of FIG. 4 , fully choked flownever actually develops for the scenarios simulated).

In the non-elastomeric, non-polymeric, non-metallic microfluidic valvestructures discussed herein, the membrane/diaphragm of a microfluidicvalve structure may be configured to have a very small actuation gap,i.e., the distance through which the diaphragm must move, in order toseal against an orifice of the valve structure and obstruct fluid flow.The actuation gap may generally be driven by the size of the diaphragm,with larger diaphragms permitting larger displacements and thus allowingfor larger actuation gaps. For example, a microfluidic valve structurehaving a silicon-based diaphragm with an effective diameter of 5 mm maybe configured to only permit 0.04 mm of deflection before sealingagainst an orifice of the valve structure. However, as mentionedearlier, for microfluidic valve structures intended to function withsemiconductor processing equipment in which the gases flowed through themicrofluidic valve structure may flow into a sub-atmosphericenvironment, the diaphragm may be exposed to a preexisting pressuredifferential when in an unactuated state, e.g., sub-atmospheric pressureon the first side of the diaphragm, and atmospheric pressure (or apressure higher than the sub-atmospheric pressure on the first side ofthe diaphragm) on the second side of the diaphragm. As a result, thediaphragm may, even when not actively actuated, be in a partiallydistended or flexed state—actuation by increasing the pressure on thesecond side of the diaphragm may simply cause the diaphragm to deflector distend further until the first side of the diaphragm contacts theraised seat structure.

This issue is peculiar to microfluidic valves in the context ofsemiconductor processing tools, and imposes some practical limitationson such valves that are not encountered in normal microfluidic systems,e.g., liquid-handling microfluidic systems as may be used for genetic,chemical, or biological fluidic analysis. For example, diaphragmdeflection as a function of constant pressure increases non-linearly inconjunction with increasing diaphragm diameter. Thus, increasing thediaphragm diameter may provide for greater potential travel allowancesin the diaphragm, but at the cost of increased “static” deflection dueto atmospheric pressure, which acts to reduce the size of the gap inbetween the diaphragm 108 and the surface 122 of the raised seatstructure that is available and which may also cause increased stressesin the diaphragm, which may lead to earlier failure. The other detrimentto increasing diaphragm diameter is that fewer microfluidic valvestructures may be manufactured at a time. As mentioned earlier,lithographic techniques may be used to manufacture the layers of themicrofluidic devices described herein. In such techniques, a largenumber of microfluidic valve structures may be manufactured on a singlewafer, e.g., a silicon wafer. Such manufacturing techniques areexpensive to implement, and become more cost-effective when largenumbers of microfluidic valve structures are manufactured simultaneouslyon one wafer. Accordingly, since fewer microfluidic valve structures canfit on a given size wafer as the diameter of the diaphragm 108 isincreased in size, it may be beneficial to reduce or minimize thediameter of the diaphragm in many implementations. In particular, thepresent inventors have found that, in some implementations, restrictingthe diameter D_(vpl) to a value on the order of a centimeter or less,e.g., 10 mm, 9 mm, 8 mm, 7 mm, 6, mm, 5 mm, 4 mm, or 3 mm, 2 mm, 1 mm,or values therebetween.

The diameter of the diaphragm, as well as the nature of the materialused to provide the diaphragm, may effectively govern the maximum amountof travel that the diaphragm may provide (without failing) when thesecond side of the diaphragm is subjected to a given pressureenvironment. This maximum amount of travel may, in turn, govern the sizeof the gap distance d, taking into account, if needed, any pre-actuationdisplacement due to atmospheric pressure effects. For example, amicrofluidic valve structure with a 5 mm diameter 85 μm thick diaphragmmay have a gap distance of 0.040 mm, although this gap distance isconservative and larger gap distances may be used in some instances,e.g., up to 0.125 mm in some implementations.

The orifice may generally be selected according to the flowcharacteristics of the gas that are desired for a given semiconductorprocessing tool utilizing the microfluidic valve structure. The orificemay have dimensions that are selected to produce choked flowtherethrough for a range of flow rates desired for a semiconductorprocessing operation provided by the semiconductor processing tool. Forexample, orifice diameters of 0.2 mm, 0.3 mm, 0.4 mm, 0.5 mm, 0.6 mm,0.7 mm, 0.8 mm, 0.9 mm, or 1 mm, or values therebetween, may be used invarious implementations.

The dimensions of the raised seat structure may be selected inaccordance with the orifice size, gap distance, and the diaphragmdiameter. For example, the inner diameter D_(i) of the raised seatstructure may be selected to be less than or equal to 0.2·D_(d), whereD_(d) is the nominal diameter of the diaphragm, e.g., D_(vpl). The innerdiameter D_(i), gap distance d, and orifice diameter D may be selectedsuch that A_(o) is less than or equal to

${\frac{\pi}{2} \cdot d \cdot D_{i}},$

where A_(o) is the cross-sectional area of the orifice, e.g., for acircular orifice, A_(o)=π·D²/4. In various implementations,

${A_{o} \leq {{\frac{\pi}{2} \cdot d \cdot D_{i}}{and}A_{o}} \geq {0.9 \cdot \frac{\pi}{2} \cdot d \cdot D_{i}}},{A_{o} \geq {0.8 \cdot \frac{\pi}{2} \cdot d \cdot D_{i}}},{A_{o} \geq {0.7 \cdot \frac{\pi}{2} \cdot d \cdot D_{i}}},{A_{o} \geq {0.6 \cdot \frac{\pi}{2} \cdot d \cdot D_{i}}},{A_{o} \geq {0.5 \cdot \frac{\pi}{2} \cdot d \cdot D_{i}}},{{{or}A_{o}} \geq {\frac{\pi}{2 \cdot 625} \cdot d \cdot {D_{i}.}}}$

The various layers of the microfluidic valve structures disclosed hereinmay be configured in a variety of different ways. For example, someimplementations may feature layers having through-features that are thenbonded to layers that do not have corresponding through-features so asto make blind holes or internal chambers within the layer stack. Inother implementations, blind holes may be formed directly in a layerwithout requiring any bonding, e.g., through etching or machining afeature to a depth that is less than the thickness of that layer. Thethicknesses of various layers may be selected as desired depending onthe needs of a particular application. For example, in some microfluidicvalve structures, the diaphragm may be between 15 μm and 120 μm thick,e.g., on the order of 0.085 mm thick; the thickness of the diaphragm, ofcourse, governs, at least in part, the travel that may be realized bythe diaphragm during actuation.

In some implementations, the base may be between 100 μm and 1000 μmthick, e.g., 0.725 mm thick; the thickness of the base may be selectedso as to be structurally able to support the raised seat structure andsurvive the operating pressures within the valve structure. However, thethickness of the base may also determine the length of the orifice; atoo-long orifice may experience an undesirable increase in flowresistance.

FIG. 5 provides a simplified perspective view of various elements of amicrofluidic valve structure as discussed above. In FIG. 5 , a diaphragm508 of diameter D_(d) is shown in conjunction with a raised seatstructure 520, which has a surface 522 that faces a first side 510 ofthe diaphragm 508 and is separated from the first side 510 by a gap ofdistance d. A second side 512 of the diaphragm 508 (the top side in FIG.5 ) may be pressurized to drive the diaphragm 508 into contact with thesurface 522 of the raised seat structure 520. The raised seat structure520 may have an inner diameter D_(i) and an outer diameter D_(o) thatmay each, in conjunction with the gap distance d, define cylindricalreference surfaces of areas A_(g1) and A_(g2), e.g., by multiplying thecircumference associated with each respective diameter by the gapdistance d. An orifice 518 may be located in a base (not picture) of themicrofluidic valve structure; the orifice may have a cross-sectionalsurface area A_(o). Generally speaking, A_(g1) may be selected to begreater than twice A_(o).

In some implementations, the diaphragm 108 may be implemented in aparticular manner, e.g., with different diameters used to define thefirst side 110 and the second side 112. For example, as shown in FigureAA, the first side 110 of the diaphragm 108, and the valve plenum 138,may be defined by the nominal diaphragm diameter D_(vpl), and the secondside 112 of the diaphragm 108, and the actuator plenum 132, may bedefined by a nominal actuator plenum diameter D_(apl). As can be seen,the actuator plenum 132 may be provided in an actuator plenum layer 134(layer 140 a), which may have a hole through it of diameter D_(vpl).Similarly, the valve plenum 138 may be provided in a valve plenum layer140 (layer 140 c), which may have a hole through it of diameter D_(apl).By avoiding a structure in which D_(vpl) and D_(apl) are the same, thestresses in the corners where the layers 140 a and 140 c meet with thelayer 140 b that provides the diaphragm 108 may be significantlyreduced, offering more robust valve operation and a lower chance ofvalve failure.

Non-elastomeric, non-polymeric, non-metallic microfluidic valvestructures such as those disclosed herein may be used in a variety ofways in semiconductor processing equipment. FIGS. 6 and 7 depict oneexample implementation in which such microfluidic valve structures maybe used. FIG. 6 depicts a diagram of a flow splitter for combining aplurality of gases together in a controllable manner. In FIG. 6 , aplurality of gas sources 630 a-630 f are provided. Each gas source 630may, for example, receive gas from a pressurized gas source or vessel.The gas sources 630 may each, in turn, be fluidically connected with aninlet gallery 642, e.g., gas source 630 a may be fluidically connectedwith inlet gallery 642 a, gas source 630 b may be fluidically connectedwith inlet gallery 642 b, and so forth. Each inlet gallery 642 may, inturn, be fluidically connected with a corresponding branch passage 646by a corresponding plurality of non-elastomeric, non-polymeric,non-metallic microfluidic valve structures 606 (only three are calledout in FIG. 6 , but it is readily apparent that there are seven suchmicrofluidic valve structures 606 for each inlet gallery 642). In thisexample, each inlet gallery is fluidically connected with sevenmicrofluidic valve structures, although it will be understood that moreor fewer such microfluidic valve structures may be provided, and thattwo or more of the gas supplies 630 may be joined with their respectivebranch passages 642 by a different number of microfluidic valvestructures 606 (rather than the same number of microfluidic valvestructures for each). The branch passages 646 may, in turn all join upat a common outlet passage 644 that may lead to a mixed gas outlet 648.

In a flow splitter such as that shown in FIG. 6 , the microfluidic valvestructures 606 may be kept in a closed state, e.g., by pressurizing thediaphragms using pneumatic valves and pressurized air, therebypreventing the process gases provided by the gas sources 630 fromflowing into the branch passages 646. If a particular combination ofprocess gases is desired in a particular mixing ratio and/or flow rate,then an appropriate number of the microfluidic valve structures 606 foreach of those gas supplies 130 may be actuated into an open state,thereby allowing those process gases to flow into their respectivebranch passages 646 and into the common outlet passage 644. For example,if a 1:3:7 ratio of gases from gas supplies 630 a, 630 c, and 630 d,respectively, is desired, then one microfluidic valve structure 606fluidically connecting the inlet gallery 642 a and the branch passage646 a may be opened, three microfluidic valve structures 606 fluidicallyconnecting the inlet gallery 642 c and the branch passage 646 c may beopened, and seven microfluidic valve structures 606 fluidicallyconnecting the inlet gallery 642 d and the branch passage 646 d may beopened. Assuming that the orifices of each microfluidic valve structure606 are the same size, the fully choked flow that may be providedthrough each orifice of each open microfluidic valve structure mayprovide the desired gas ratio.

FIG. 7 depicts an example of a two-source flow splitter. In FIG. 7 , twogas sources 730 a and 730 b are connected to respective pressurized gassupplies and supply corresponding process gases to inlet galleries 742 aand 742 b, respectively. Each inlet gallery 742 is, in turn fluidicallyconnected with a common outlet passage 744 by a plurality ofcorresponding microfluidic valve structures 706 a and 706 b. The commonoutlet passage 744 leads to a mixed gas outlet 748. In this particularexample, instances A and B of the microfluidic valve structures 706 aare in an open state (this may be the default, unactuated state in someimplementations), whereas instances C, D, E, F, and G of themicrofluidic valve structures 706 a are in a closed state. Similarly,instances A, B, C, and D of the microfluidic valve structures 706 b arein an open state, whereas instances E, F, and G of the microfluidicvalve structures 706 a are in a closed state. Thus, the mixing ratio ofgas from the gas source 730 a to the gas source 730 b may be 1:2.

It will be recognized that many other implementations of microfluidicvalve structures may be practiced using the microfluidic valvestructures disclosed in this application. For example, one suchimplementation is a semiconductor processing showerhead, e.g., a gasdistributor that distributes processing gases over a semiconductor waferduring processing operations. Showerheads typically have a large number,e.g., hundreds or thousands, of gas distribution ports spread across theunderside of the showerhead—an area that is generally at least as largein diameter as the wafer being processed. Process gas flows through theshowerhead are typically regulated by valves that are located outside ofthe showerhead. For externally located valves, there may be asignificant delay, e.g., some seconds, between when the valve is openedand the gas flowing therethrough is released by the showerhead (thisdelay is due to the need for the gas to flow from the valve, through theshowerhead, and through the gas distribution ports on the underside (orfaceplate) of the showerhead. There may also be a significant amount ofwasted gas trapped within the showerhead after each gas flow.

As discussed in U.S. patent application Ser. No. 15/346,920, filed Nov.11, 2016, a more effective showerhead may be provided by implementingmicrofluidic valve structures, such as those disclosed herein, withinthe showerhead, e.g., at each gas distribution port. In this manner, theflow path from each microfluidic valve structure to gas distributionport may generally be as short as is feasible, thereby reducing transittime for the gases released thereby. In some implementations, eachmicrofluidic valve structure, or groups of such valve structures, may beseparately actuable, thereby allowing groups of valves to be actuated orunactuated and allowing different flow patterns of gas to be provided bythe showerhead. It will be understood that the microfluidic valvestructures discussed herein may be used to provide the valves for theactive showerheads discussed in U.S. patent application Ser. No.15/346,920, the contents of which are hereby incorporated by referencein their entirety.

As mentioned above, the microfluidic valve structures discussed hereinmay be actuated by any suitable mechanism, e.g., through actuation ofpneumatic valves that may be used to pressurize the diaphragms of suchvalve structures. Such pneumatic valves may be controlled by acontroller of a semiconductor processing tool. The controller may bepart of a system that may include semiconductor processing equipment,including a processing tool or tools, chamber or chambers, platform orplatforms for processing, and/or specific processing components (a waferpedestal, a gas flow system, etc.). These systems may be integrated withelectronics for controlling their operation before, during, and afterprocessing of a semiconductor wafer or substrate. The electronics may bereferred to as the “controller,” which may control various components orsubparts of the system or systems. The controller, depending on theprocessing requirements and/or the type of system, may be programmed tocontrol any of the processes disclosed herein, as well as variousparameters affecting semiconductor processing, such as the delivery ofprocessing gases, temperature settings (e.g., heating and/or cooling),pressure settings, vacuum settings, power settings, radio frequency (RF)generator settings, RF matching circuit settings, frequency settings,flow rate settings, fluid delivery settings, positional and operationsettings, wafer transfers into and out of a tool and other transfertools and/or load locks connected to or interfaced with a specificsystem.

Broadly speaking, the controller may be defined as electronics havingvarious integrated circuits, logic, memory, and/or software that receiveinstructions, issue instructions, control operation, enable cleaningoperations, enable endpoint measurements, and the like. The integratedcircuits may include chips in the form of firmware that store programinstructions, digital signal processors (DSPs), chips defined asapplication specific integrated circuits (ASICs), and/or one or moremicroprocessors, or microcontrollers that execute program instructions(e.g., software). Program instructions may be instructions communicatedto the controller in the form of various individual settings (or programfiles), defining operational parameters for carrying out a particularprocess on or for a semiconductor wafer or to a system. The operationalparameters may, in some embodiments, be part of a recipe defined byprocess engineers to accomplish one or more processing steps during thefabrication of one or more layers, materials, metals, oxides, silicon,silicon dioxide, surfaces, circuits, and/or dies of a wafer.

The controller, in some implementations, may be a part of or coupled toa computer that is integrated with, coupled to the system, otherwisenetworked to the system, or a combination thereof. For example, thecontroller may be in the “cloud” or all or a part of a fab host computersystem, which can allow for remote access of the wafer processing. Thecomputer may enable remote access to the system to monitor currentprogress of fabrication operations, examine a history of pastfabrication operations, examine trends or performance metrics from aplurality of fabrication operations, to change parameters of currentprocessing, to set processing steps to follow a current processing, orto start a new process. In some examples, a remote computer (e.g. aserver) can provide process recipes to a system over a network, whichmay include a local network or the Internet. The remote computer mayinclude a user interface that enables entry or programming of parametersand/or settings, which are then communicated to the system from theremote computer. In some examples, the controller receives instructionsin the form of data, which specify parameters for each of the processingsteps to be performed during one or more operations. It should beunderstood that the parameters may be specific to the type of process tobe performed and the type of tool that the controller is configured tointerface with or control. Thus as described above, the controller maybe distributed, such as by comprising one or more discrete controllersthat are networked together and working towards a common purpose, suchas the processes and controls described herein. An example of adistributed controller for such purposes would be one or more integratedcircuits on a chamber in communication with one or more integratedcircuits located remotely (such as at the platform level or as part of aremote computer) that combine to control a process on the chamber.

Without limitation, example systems may include a plasma etch chamber ormodule, a deposition chamber or module, a spin-rinse chamber or module,a metal plating chamber or module, a clean chamber or module, a beveledge etch chamber or module, a physical vapor deposition (PVD) chamberor module, a chemical vapor deposition (CVD) chamber or module, anatomic layer deposition (ALD) chamber or module, an atomic layer etch(ALE) chamber or module, an ion implantation chamber or module, a trackchamber or module, and any other semiconductor processing systems thatmay be associated or used in the fabrication and/or manufacturing ofsemiconductor wafers.

As noted above, depending on the process step or steps to be performedby the tool, the controller might communicate with one or more of othertool circuits or modules, other tool components, cluster tools, othertool interfaces, adjacent tools, neighboring tools, tools locatedthroughout a factory, a main computer, another controller, or tools usedin material transport that bring containers of wafers to and from toollocations and/or load ports in a semiconductor manufacturing factory.

The term “wafer,” as used herein, may refer to semiconductor wafers orsubstrates or other similar types of wafers or substrates. A waferstation, as the term is used herein, may refer to any location in asemiconductor processing tool in which a wafer may be placed during anyof various wafer processing operations or wafer transfer operations.Wafer support is used herein to refer to any structure in a waferstation that is configured to receive and support a semiconductor wafer,e.g., a pedestal, an electrostatic chuck, a wafer support shelf, etc.

It is also to be understood that the use of ordinal indicators, e.g.,(a), (b), (c), . . . , herein is for organizational purposes only, andis not intended to convey any particular sequence or importance to theitems associated with each ordinal indicator. For example, “(a) obtaininformation regarding velocity and (b) obtain information regardingposition” would be inclusive of obtaining information regarding positionbefore obtaining information regarding velocity, obtaining informationregarding velocity before obtaining information regarding position, andobtaining information regarding position simultaneously with obtaininginformation regarding velocity. There may nonetheless be instances inwhich some items associated with ordinal indicators may inherentlyrequire a particular sequence, e.g., “(a) obtain information regardingvelocity, (b) determine a first acceleration based on the informationregarding velocity, and (c) obtain information regarding position”; inthis example, (a) would need to be performed (b) since (b) relies oninformation obtained in (a)-(c), however, could be performed before orafter either of (a) or (b).

It is to be understood that use of the word “each,” such as in thephrase “for each <item> of the one or more <items>” or “of each <item>,”if used herein, should be understood to be inclusive of both asingle-item group and multiple-item groups, i.e., the phrase “for . . .each” is used in the sense that it is used in programming languages torefer to each item of whatever population of items is referenced. Forexample, if the population of items referenced is a single item, then“each” would refer to only that single item (despite the fact thatdictionary definitions of “each” frequently define the term to refer to“every one of two or more things”) and would not imply that there mustbe at least two of those items. Similarly, when a selected item may haveone or more sub-items and a selection of one of those sub-items is made,it will be understood that in the case where the selected item has oneand only one sub-item, selection of that one sub-item is inherent in theselection of the item itself.

It will also be understood that references to multiple controllers thatare configured, in aggregate, to perform various functions are intendedto encompass situations in which only one of the controllers isconfigured to perform all of the functions disclosed or discussed, aswell as situations in which the various controllers each performsubportions of the functionality discussed. For example, anautocalibration wafer may include a controller that is configured tocontrol the operation of the various sensors on the autocalibrationwafer and communicate data therefrom to another controller associatedwith a semiconductor processing tool; the semiconductor processing toolcontroller may then analyze such data to determine various operationalparameters for use with the semiconductor processing tool.

Various modifications to the implementations described in thisdisclosure may be readily apparent to those skilled in the art, and thegeneric principles defined herein may be applied to otherimplementations without departing from the spirit or scope of thisdisclosure. Thus, the claims are not intended to be limited to theimplementations shown herein, but are to be accorded the widest scopeconsistent with this disclosure, the principles and the novel featuresdisclosed herein.

Certain features that are described in this specification in the contextof separate implementations also can be implemented in combination in asingle implementation. Conversely, various features that are describedin the context of a single implementation also can be implemented inmultiple implementations separately or in any suitable sub-combination.Moreover, although features may be described above as acting in certaincombinations and even initially claimed as such, one or more featuresfrom a claimed combination can in some cases be excised from thecombination, and the claimed combination may be directed to asub-combination or variation of a sub-combination.

Similarly, while operations are depicted in the drawings in a particularorder, this should not be understood as requiring that such operationsbe performed in the particular order shown or in sequential order, orthat all illustrated operations be performed, to achieve desirableresults. Further, the drawings may schematically depict one more exampleprocesses in the form of a flow diagram. However, other operations thatare not depicted can be incorporated in the example processes that areschematically illustrated. For example, one or more additionaloperations can be performed before, after, simultaneously, or betweenany of the illustrated operations. In certain circumstances,multitasking and parallel processing may be advantageous. Moreover, theseparation of various system components in the implementations describedabove should not be understood as requiring such separation in allimplementations, and it should be understood that the described programcomponents and systems can generally be integrated together in a singlesoftware product or packaged into multiple software products.Additionally, other implementations are within the scope of thefollowing claims. In some cases, the actions recited in the claims canbe performed in a different order and still achieve desirable results.

What is claimed is:
 1. An apparatus comprising: a substrate having oneor more microfluidic valve structures, each microfluidic valve structureof the one or more microfluidic valve structures including: a diaphragmhaving a first side, and a second side opposite the first side; a base;an orifice in the base; and a raised seat structure, wherein, for eachmicrofluidic valve structure: the diaphragm is made from anon-elastomeric material, the raised seat structure extends from thebase towards the first side of the diaphragm, a surface of the raisedseat structure facing the diaphragm is separated from the first side ofthe diaphragm by a gap when the microfluidic valve structure is in anunactuated state, and the diaphragm, the raised seat structure, and thegap of that microfluidic valve structure are sized such that, when thatmicrofluidic valve structure is transitioned to an actuated state bypressurizing the second side of the diaphragm to a first pressure, aportion of the diaphragm is caused to elastically deform towards, andseal against, the raised seat structure.
 2. The apparatus of claim 1,wherein the diaphragm is made of a non-polymeric, non-elastomericmaterial.
 3. The apparatus of claim 2, wherein the raised seat structureand the base are also made of non-polymeric, non-elastomeric material ormaterials.
 4. The apparatus of claim 1, wherein the diaphragm is made ofa non-metallic, non-elastomeric material.
 5. The apparatus of claim 4,wherein the raised seat structure and the base are also made ofnon-metallic, non-elastomeric material or materials.
 6. The apparatus ofclaim 1, wherein the diaphragm is made of a non-polymeric, non-metallic,non-elastomeric material.
 7. The apparatus of claim 6, wherein theraised seat structure and the base are also made of non-polymeric,non-metallic, non-elastomeric material or materials.
 8. The apparatus ofclaim 6, wherein the non-polymeric, non-metallic, non-elastomericmaterial comprises silicon.
 9. The apparatus of claim 6, wherein thenon-polymeric, non-metallic, non-elastomeric material comprises silicondioxide.
 10. The apparatus of claim 1, wherein: the substrate includes afirst inlet passage and a first outlet passage, the one or moremicrofluidic valve structures includes a first set of microfluidic valvestructures, each microfluidic valve structure in the first set ofmicrofluidic valve structures is fluidically interposed between thefirst inlet passage and the first outlet passage, and the orifice ineach microfluidic valve structure in the first set of microfluidic valvestructures is fluidically interposed between the first inlet passage andthe diaphragm of that microfluidic valve structure.
 11. The apparatus ofclaim 10, wherein each microfluidic valve structure in the first set ofmicrofluidic valve structures is independently actuatable from eachother microfluidic valve structure in the first set of microfluidicvalve structures.
 12. The apparatus of claim 10, wherein: the substratefurther includes one or more additional inlet passages, the substratefurther includes a corresponding additional outlet passage for eachadditional inlet passage, the one or more microfluidic valve structuresincludes a corresponding set of microfluidic valve structures for eachadditional inlet passage, each microfluidic valve structure in each setof microfluidic valve structures corresponding to one of the one or moreadditional inlet passages is fluidically interposed between thatadditional inlet passage and the corresponding outlet passage, and theorifice in each microfluidic valve structure in each set of microfluidicvalve structures corresponding to one of the one or more additionalinlet passages is fluidically interposed between that additional inletpassage and the diaphragm of that microfluidic valve structure.
 13. Theapparatus of claim 12, wherein each microfluidic valve structure in thecorresponding set of microfluidic valve structures for each additionalinlet passage is independently actuatable relative to each othermicrofluidic valve structure in the corresponding set of microfluidicvalve structures for that additional inlet passage.
 14. The apparatus ofclaim 12, wherein: the first outlet passage and each additional outletpassage branch off of a common outlet passage, the first outlet passageis fluidically interposed between the common outlet passage and themicrofluidic valve structures in the first set of microfluidic valvestructures, and each additional outlet passage is fluidically interposedbetween the common outlet passage and the microfluidic valve structuresin the set of microfluidic valve structures corresponding to theadditional inlet passage that corresponds to that additional outletpassage.
 15. The apparatus of claim 10, wherein: the substrate includesa second inlet passage, the one or more microfluidic valve structuresincludes a second set of microfluidic valve structures, eachmicrofluidic valve structure in the second set of microfluidic valvestructures is fluidically interposed between the second inlet passageand the first outlet passage, and the orifice in each microfluidic valvestructure in the second set of microfluidic valve structures isfluidically interposed between the second inlet passage and thediaphragm of that microfluidic valve structure.
 16. The apparatus ofclaim 15, wherein: each microfluidic valve structure in the first set ofmicrofluidic valve structures is independently actuatable from eachother microfluidic valve structure in the first set of microfluidicvalve structures, and each microfluidic valve structure in the secondset of microfluidic valve structures is independently actuatable fromeach other microfluidic valve structure in the second set ofmicrofluidic valve structures.
 17. The apparatus of claim 1, furthercomprising: a diaphragm layer; an actuator plenum layer; and a valveplenum layer, wherein: the diaphragm of a first microfluidic valvestructure of the one or more microfluidic valve structures is providedby the diaphragm layer, a first side of the diaphragm layer provides thefirst side of the diaphragm of the first microfluidic valve structure, asecond side of the diaphragm layer provides the second side of thediaphragm of the first microfluidic valve structure, the first side ofthe diaphragm layer is bonded to the valve plenum layer, the second sideof the diaphragm layer is bonded to the actuator plenum layer, theactuator plenum layer has a hole through it that is centered on thediaphragm of the first microfluidic valve structure, and the valveplenum layer has a hole through it that is also centered on thediaphragm of the first microfluidic valve structure.
 18. The apparatusof claim 1, further comprising a showerhead with a plurality of gasdistribution ports distributed across an underside thereof, wherein atleast one of the one or more microfluidic valve structures is configuredto control flow of gas through a corresponding one of the gasdistribution ports and is positioned within the showerhead.
 19. Theapparatus of claim 18, further comprising a processing chamber, whereinthe underside of the showerhead is configured to distribute gas flowedthrough the gas distribution ports into the processing chamber.
 20. Theapparatus of claim 1, wherein the apparatus is configured to beconnected to a gas supply such that at least a first microfluidic valvestructure of the one or more microfluidic valve structures is part of aflow path within the apparatus that is configured to be fluidicallyconnectable with the gas supply such that the raised seat structure forthe first microfluidic valve structure is fluidically interposed betweenthe gas supply and the diaphragm for the first microfluidic valvestructure.